1. Technical Field
The present invention relates to an atomic oscillator.
2. Related Art
An atomic oscillators using transition energy of atoms as reference frequency is widely used as one of highest-precision oscillators in communication base stations or the like. Although there are several types as the atomic oscillator, a microwave double resonance type using a rubidium (Rb) lamp is most generally used.
In recent years, an atomic oscillator using a phenomenon called Coherent Population Trapping (CPT) that is one of quantum interference effects is suggested (for example, refer to JP-A-2015-62167), and reduced size and low power consumption of the atomic oscillator are expected compared with the related art. In the case of the CPT type, sidebands are used for development of a CPT phenomenon by superimposing a high-frequency signal using a coherent light source, such as a laser, as a light source. The CPT type atomic oscillator is an oscillator using an electromagnetically induced transparency (EIT) phenomenon in which if alkali metal atoms are irradiated with coherent light having two different kinds of wavelength (frequency), the absorption of the coherent light stops.
In order to develop the CPT phenomenon as the light source of the atomic oscillator, high-precision adjustment of the output wavelength of a laser element or the like is required. If an inflow current to the laser element or the like is changed, it is possible to adjust the output wavelength.
However, if the inflow current to the laser element is changed, the optical output of the laser element or the like varies simultaneously. Therefore, it is necessary to form a control loop of the atomic oscillator in consideration of this, and complicated control is required. Therefore, a light source that can control its output wavelength and optical output individually is needed.